1. Field
The presently disclosed subject matter relates to semiconductor light-emitting devices in which light emitted from a semiconductor light-emitting chip is wavelength-converted by a wavelength converting layer, to manufacturing methods for the same and to vehicle headlights. More particularly, the disclosed subject matter relates to reliable semiconductor light-emitting devices for a vehicle headlight and the like, which can be maintained at a high quality even when they have been used for a long time under a harsh condition, and to methods of manufacturing such devices, and further to vehicle headlights using the devices.
2. Description of the Related Art
Semiconductor light-emitting devices, in which a part of the light emitted from a semiconductor light-emitting chip is converted into light having a different wavelength by a phosphor and in which a mixture light including the light having the different wavelength mixed with the light emitted directly from the semiconductor light-emitting chip is emitted, have been known as a semiconductor light source for various lighting units. In these conventional cases, the semiconductor light-emitting devices are frequently provided with a wavelength converting layer composed of a resin layer including a phosphor particle on or over the semiconductor light-emitting chip such as an LED chip, etc.
Conventional semiconductor light-emitting devices including such a wavelength converting layer are disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2010-192629) and Patent Document No. 2 (Japanese Patent Application Laid Open JP2010-219324). FIGS. 13a and 13b are, respectively, a top view, and a side cross-sectional view taken along line A-A in FIG. 13a, showing a conventional semiconductor light-emitting device, which may be used as a light source for general lighting and the like and which is disclosed in Patent Document No. 2.
The conventional semiconductor light-emitting device 300 includes: a mounting board 50; a conductor pattern 51 formed on the mounting board 50; a frame 55 formed in a tubular shape and being located on the mounting board 50; a semiconductor light-emitting chip 60 mounted on the conductor pattern 51: an optical transparent material 70 including a wavelength converting layer and being located on the semiconductor light-emitting chip 60 via a light-transmitting material 80; a sealing material 40 including a light-reflecting material 45 and being disposed between the frame 55 and at least the optical transparent material 70; and a light-emitting surface 90 exposed from a top surface of the optical transparent material 70 as a light-emitting surface of the device 300 so as to be able to emit a wavelength converted light.
When carrying out a reliability test such as when conventional devices having a structure such as the above-described semiconductor light-emitting device 300 are caused to emit light continuously for a long time in a closed box, the light-reflecting material 45 dispersed in the sealing material 40 may be extremely overheated by high heat generated from the semiconductor light-emitting chip 60, and light emitted the semiconductor light-emitting chip 60 may cause a photocatalytic action which may result in a hydrophilic property.
As a result, the high heat and the light may cause an oil-bleeding phenomenon such that a liquid component exudes from the sealing material 40 toward an outside surface thereof. When an amount of the liquid component is large, the liquid components may not stay near the outside surface of the sealing material 40, and therefore may flow toward the light-emitting surface 90 of the semiconductor light-emitting device 300 and toward the frame 55.
Accordingly, the oil-bleeding phenomenon may degrade not only an outside appearance of the light-emitting device but also optical characteristics of the light-emitting device such as a light-emitting intensity, a light distribution pattern, a chromaticity distribution, etc. When the semiconductor light-emitting device is used as a light source for a headlight such that may be used for a long time under harsh conditions, a headlight using the semiconductor light-emitting device may not conform to a vehicle standard for a headlight. The light when configured as a headlight also may affect driving performance, in the worst case.
In addition, when the semiconductor light-emitting device is used as a light source for a tunnel lighting unit such that light must be emitted at any time of night or day under harsh conditions, the semiconductor light-emitting device may also be subject to the oil-bleeding phenomenon such that the light may degrade in terms of the optical characteristics of the light-emitting device. If the liquid components flow toward the light-emitting surface of the semiconductor light-emitting device, the tunnel lighting unit may also deteriorate and affect driving performance, at the worst.
The above-referenced Patent Documents are listed below, and are hereby incorporated with their English abstracts in their entireties.    1. Patent Document No. 1: Japanese Patent Application Laid Open JP2010-192629    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2010-219324    3. Patent Document No. 3: U.S. patent application Ser. No. 13/229,663 published as U.S. Patent Publication No. 2012/0235169 A1.    4. Patent Document No. 4: U.S. patent application Ser. No. 12/903,200 (ST3001-0270) published as U.S. Patent Publication No. 2011/0084299 A1.    5. Patent Document No. 5: U.S. patent application Ser. No. 13/196,868 published as U.S. Patent Publication No. 2012/0025218 A1.
The presently disclosed subject matter has been devised to consider the above and other problems, features, and characteristics in the conventional art devices. Embodiments of the disclosed subject matter can include semiconductor light-emitting devices that can emit a wavelength converted light having a high reliability and a high light-emitting efficiency from a small light-emitting surface, and associated manufacturing methods that do not cause and/or are designed to prevent some of the above-described problems, concerns, and characteristics related to a light-emitting surface. The disclosed subject matter can also include a vehicle headlight using the semiconductor light-emitting device that can form a light distribution pattern including a horizontal cut-off line with a simple structure, and which can be maintained at a high quality even when it has been used for a long time under a harsh condition.